A Microsoft file hosting and synchronization service.
Given the symptoms, the most relevant supported path is to rule out policy blocking, then reset or reinstall OneDrive, and if sign-in/account state is involved, clear account identity conflicts.
- Check whether OneDrive is being blocked by policy.
- Open Registry Editor.
- Go to:
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\OneDrive - Check whether
DisableFileSyncNGSCis set toDWORD:1. - If it is, OneDrive for work or school is prevented from starting. The correct fix is to have the applicable Group Policy removed or changed.
- Run Microsoft Support and Recovery Assistant.
This is the documented first step when sign-in or sync conflicts may be involved.
- Install Microsoft 365 Support and Recovery Assistant.
- Select OneDrive for Business.
- Select I need help syncing my OneDrive files.
- If the assistant does not fix it, reset OneDrive. Microsoft documents reset as a next step for sign-in and sync issues. A reset clears OneDrive settings and triggers a full sync afterward.
- If reset does not help, uninstall and reinstall OneDrive.
- In Windows, open Add or remove programs.
- Under Apps & features, select Microsoft OneDrive.
- Select Uninstall.
- Install the latest OneDrive app again.
- If multiple work or old accounts have been used on these devices, unlink and relink the correct account. Microsoft identifies account/configuration problems and multiple identities as causes for sign-in failures such as 0x8004de80 or 0x8004de86.
- If account identity conflicts remain, clear cached Office account identities from the registry. This is the documented remediation when multiple identities are causing OneDrive sign-in issues.
- If repair has not already been tried, repair Office before another uninstall/reinstall cycle. Microsoft notes that repairing Office can often resolve OneDrive for work or school issues without requiring uninstall and reinstall.
- If the issue still persists on all three Surface Pro 9 devices after the above, create a Microsoft support incident. The troubleshooting guidance explicitly recommends opening a support case when the documented self-help path does not resolve the problem.
The Event ID 1000 crash details and the specific ucrtbase.dll / 0xc0000409 combination are not covered in the available documentation, so the supported guidance is the remediation path above rather than a crash-specific root cause.